I just listened to a podcast that discussed using M:tG Praetors as boss villains in D&D, and that led to a question in my mind: would Praetors make good icons in 13th Age? Are they powerful enough, with widespread influence, and conflict between them? I'm not sure of the answer, given the limited coverage of the topic on the podcast, so I thought I'd reach out to the community. What do you think?

Thanks for the links! With each of the Praetors appearing to fall somewhere in the evil side of the spectrum (at least based on their descriptions in the podcast I listened to), are there any powerful "good guys" in the setting? "Ambiguously gray" boss-level characters?

Skimming through that first article, it looks like the M:tG designers have added one Praetor per faction. But would each one oppose all other Praetors of other colours?

I know there are more than five planes in the M:tG universe. So what is the deal with the planes? Does one Praetor influence lots of different planes that use the same colour of magic? Or do the Praetors only have power over a small area?

Or are there additional Praetors (one per plane) that have power locally)?

Skimming through that first article, it looks like the M:tG designers have added one Praetor per faction. But would each one oppose all other Praetors of other colours?

As a general rule, yes. The five colors of magic are each allied to two others and opposed to two others, in a continuous wheel. Each represents a particular vision for Phyrexian perfection, and two praetors might make a temporary alliance against a third who is clearly "worst of the worst" to both of them (eg White+Blue against Red), but ultimately the wishes of each praetor are incompatible with any of the others. For example, Black wants there to be one singular being ruling over all Phyrexians (the black praetor Sheoldred being the current favorite candidate, although several rivals are constantly trying for her spot), while White wishes to make all Phyrexians equal in obedience to an unchanging legalistic code, and the white praetor Elesh Norn is simply the arbiter of those rules, and would not regard himself as being above them (or at least would publically claim that this was the case). Whether the Blue praetor sides with Norn or Sheoldred would depend a lot on the circumstances; Blue neither wants to bow before Black's tyrant nor White's rules, so it would likely side with whichever one seemed weaker, just to keep the two of them in conflict while continuing its own agenda.

I know there are more than five planes in the M:tG universe. So what is the deal with the planes? Does one Praetor influence lots of different planes that use the same colour of magic? Or do the Praetors only have power over a small area?

New Phyrexia, formerly known as Mirrodin, is one plane. The original Phyrexia was a different plane, artificial and since destroyed. There are an arbitrarily large if not truly infinite number of planes in the MTG multiverse, although only twenty or so have been extensively detailed and another thirty-ish mentioned in brief. I believe I made a list on this board at one point, if anyone could manage to find it (given that our search function was interrupted back when we moved).

Or are there additional Praetors (one per plane) that have power locally)?

So far, the New Phyrexians haven't made it off Mirrodin, but it's only a matter of time until they manage to create a device for traveling off-plane (unless they destroy themselves first, but that's not going to happen, just because they're too useful as villains in the storyline to be allowed to off themselves, even if that's realistically what should happen with such a psychotic "civilization" - see also the Drow). If they did manage to invade a new plane, it's likely that plane would have multiple praetors - not necessarily one per color, but one per faction, with various possible faction breakdowns. (NP itself did have factions besides the main five, but none were powerful enough to assert themselves as anything resembling equal rivals to the five color-based ones. However, this was far from the only way it could have been broken down, and if they revisit the concept in an upcoming storyline, I hope they won't repeat themselves this much.)

Thanks for the links! With each of the Praetors appearing to fall somewhere in the evil side of the spectrum (at least based on their descriptions in the podcast I listened to), are there any powerful "good guys" in the setting? "Ambiguously gray" boss-level characters?

New Phyrexia is explicitly a plane which has fallen completely to Evil (there might be a tiny handful of survivors, but they clearly have no hope of beating back the villainous horde, and are just trying to escape their own torture and conversion into monsters). Magic in general has a few characters like these, but the only powerful force for Good on the former Mirrodin was its creator, the golem-planeswalker Karn, and he left the plane as soon as he shook off the Praetors' attempts to convert him. The only vaguely powerful being that remains on NP today is the Mirrodian Planeswalker Koth, and frankly it's unlikely that he'll escape the Phyrexians for much longer, given his bullheaded refusal to accept that his homeland is obviously lost.